Radial shaft seal, radial shaft seal assembly and method of installation

ABSTRACT

A radial shaft seal configured for receipt in a housing and about a shaft to sealingly isolate an air side of the seal from an oil side of the seal is provided. The seal includes a mounting portion and a seal lip having a sealing surface extending between an oil side end and a free air side end. An annular bridge is connected to the oil side end of the seal lip by a first hinge and to the mounting portion by a second hinge. The bridge extends in radially overlying relation to the seal lip. A projection extends from the first hinge away from the bridge. A plurality of ribs extend radially inwardly from the projection. The ribs minimize friction between the seal and the shaft during installation and prevent the seal lip from inverting during the oil-side installation assembly.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates generally to dynamic oil seals of the type forcreating a fluid tight seal between a rotating shaft and a housing.

2. Related Art

Dynamic radial shaft oil seals are designed to have a so-called “oilside” of the seal and an “air side.” These designations pertain to theorientation of the seal when installed, with the oil side facing theinterior of the housing and in communication with the oil, whereas theair side faces outwardly and is exposed to the air.

There are at least two different ways in which a radial shaft oil sealcan be installed. An “air side installation” is one in which the seal isfirst installed into the bore of the housing and the shaft (or its wearsleeve) thereafter installed from the air side axially into the sealassembly (in the direction inward of the housing) to effect the seal. An“oil side installation” is the other where the housing and shaft arealready present and the seal assembly is slid axially into the housingand simultaneously onto the shaft (or its wear sleeve), such that theshaft enters the seal assembly from the oil side of the seal. Otherwise,“oil-side” installation requires the seal assembly to be installed intothe housing, also referred to as carrier, and then the housing, withseal installed therein, is assembled to an engine over the “all ready inplace” shaft.

During installation, regardless of the type, the seals must be able towithstand the axial loads resulting during installation without causinga seal lip of the seal to reverse fold or otherwise become displaced toa position where the seal lip is ineffective in the fully installedcondition. The axial load imparted on the seal lip is largely due to thefriction between the seal lip and an outer surface of the shaft as thetwo are moved axially relative to one another during installation.Accordingly, it is desirable to minimize the friction generated duringinstallation of the shaft through the seal, however, a delicate balanceneeds to be maintained in order to attain the desired seal between theseal lip and the shaft.

SUMMARY OF THE INVENTION

In general terms, this invention provides a radial shaft seal assemblyhaving features that facilitate making a proper oil side installation,even in conditions of shaft-to-bore misalignment, and further, providesupport for a seal lip of the seal assembly against adverseseal-breaking movement when exposed to positive or negative pressure onan oil side of the seal assembly when installed.

In accordance with one presently preferred aspect of the invention, aradial shaft seal configured for receipt in a housing and about a shaftto sealingly isolate an air side of the shaft seal from an oil side ofthe shaft seal is provided. The radial shaft seal includes an annularmounting portion and a seal lip having an annular sealing surfaceextending between an oil side end and a free air side end, with thesealing surface being configured to extend axially relative to theshaft. Further, an annular bridge is connected to the oil side end ofthe seal lip by a first hinge and to the mounting portion by a secondhinge. The bridge extends from the first hinge to the second hinge inradially overlying relation to the seal lip. A projection extends fromthe first hinge away from the bridge toward the oil side of the seal.The projection has a radially inwardly facing inner surface. A pluralityof circumferentially spaced ribs extend radially inwardly from the innersurface of the projection. The projection and ribs prevent the seal lipfrom inverting during the oil-side installation process, therebyensuring that the seal lip attains its proper sealing contact with arunning surface during use.

In accordance with another aspect of the invention, a radial shaft sealassembly is provided. The radial shaft seal assembly includes a shaftextending along a central axis and providing a running surface with apredetermined diameter and a radial shaft seal configured for receipt ina housing and about the shaft to sealingly isolate an air side of theradial shaft seal from an oil side of the radial shaft seal. The radialshaft seal includes an annular mounting portion and a seal lip having anannular sealing surface and an opposite backing surface extendingbetween an oil side end and a free air side end, with the sealingsurface being configured to extend axially in dynamic sealing contactwith the running surface. Further, an annular bridge is attached to theoil side end of the seal lip by a first hinge and to the mountingportion by a second hinge. The bridge extends from the first hinge tothe second hinge in radially overlying relation to the seal lip. Inaddition, at least one projection extends axially from the first hingetoward the oil side of the seal. The projection has a radially inwardlyfacing inner surface. A plurality of circumferentially spaced ribsextend radially inwardly from the inner surface of the projection. Theprojection and ribs prevent the seal lip from inverting during theoil-side installation process, thereby ensuring that the seal lipattains its proper sealing contact with a running surface during use.

In accordance with another aspect of the invention, a method ofinstalling a radial shaft seal onto a shaft is provided. The methodincludes providing a shaft having a running surface and providing theradial shaft seal with a seal lip having an annular sealing surfaceconverging from an oil side end to a free air side end while in a freestate. Further, providing the radial shaft seal with an annular bridgeattached to the oil side end by a first hinge with the bridge divergingto a second hinge while in the free state. The second hinge beingattached to an outer mounting portion such that the bridge extends inradially overlying relation with the seal lip. The radial shaft sealfurther including at least one projection extending axially from thefirst hinge toward an oil side of the seal. The projection has aradially inwardly facing inner surface, wherein a plurality ofcircumferentially spaced ribs are provided to extend radially inwardlyfrom the inner surface. Then, moving the shaft and the radial shaft sealaxially toward one another and bringing the oil side end of the seal lipinto abutment with an end of the shaft. Further, bringing the ribs intocontact with running surface of the shaft while substantially avoidingcontact of the inner surface of the projection with the shaft andbringing the sealing surface into sealing engagement with the runningsurface while simultaneously moving the ribs out of contact with therunning surface.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of the invention willbecome more readily appreciated when considered in connection with thefollowing detailed description of presently preferred embodiments andbest mode, appended claims and accompanying drawings, in which:

FIG. 1 is a plan view of a radial shaft seal constructed according toone aspect of the invention;

FIG. 2 is a cross-sectional view taken generally along the line 2-2 ofFIG. 1;

FIGS. 3-5 are cross-sectional views of the seal of FIG. 1 shown disposedin a housing with a shaft being installed in progression from anoil-side of the seal;

FIG. 6 is a cross-sectional view of a radial shaft seal constructedaccording to another aspect of the invention;

FIGS. 7-12 illustrate cross-sectional views of the seal of FIG. 5 showndisposed in a housing with a shaft being installed in progression froman oil-side of the seal in co-axially aligned relation with the seal;

FIGS. 13-19 illustrate cross-sectional views of the seal of FIG. 6 showndisposed in a housing with a shaft being installed in progression froman oil-side of the seal in axially misaligned relation with the seal;

FIG. 20 is a plan view of a radial shaft seal constructed according toanother aspect of the invention;

FIG. 21 is a cross-sectional view taken generally along the line 21-21of FIG. 20;

FIGS. 22-24 are cross-sectional views of the seal of FIG. 20 showndisposed in a housing with a shaft being installed in progression froman oil-side of the seal; and

FIG. 25 is a partial perspective view of a radial shaft seal constructedaccording to yet another aspect of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring in more detail to the drawings, FIG. 1 illustrates a radialshaft seal, referred to hereafter as seal 10, constructed in accordancewith one aspect of the invention, wherein the seal is suitable for usein a crankcase application, by way of example and without limitation,for sealing about a rotatable shaft 12 in a radial shaft seal assembly13 (FIGS. 3-5) extending through a bore 14 in the crankcase 16 in whichthe seal 10 is installed. Otherwise, the seal 10 can be installed into acarrier housing, whereupon the carrier housing and seal 10 can beattached to the engine. With reference to FIG. 2, the seal 10 has an oilside O and an axially opposite air side A, in relation to theorientation of the seal 10 when installed, with the oil side O facing tothe interior of the crankcase 16 and the air side A facing to theoutside environment. The seal 10 includes a mounting portion, such as acase, also referred to as core or collar 18, provided as a metal annulusor ring structure with an elastomeric seal material 20 attached thereto.The seal material 20 forms at least part of the an elastomeric seal body22 with an axially extending seal lip 24 that exhibits low dynamicfrictional contact with the shaft 12 during use, thereby resulting in alow torque between the shaft 12 and the seal lip 24, such as betweenabout 0.07-0.35 N*m (Newton meters), as newly installed, during and uponuse. Accordingly, as a result of the minimal frictional losses exhibitedby the seal 10, the losses in efficiency of the engine are kept to aminimum.

The annular metal collar 18 may be L-shaped, as illustrated, or may takeon any number of configurations, such as ring-shaped, C-shaped orS-shaped, depending upon the requirements of a particular application,as is know in the art. The L-shaped collar 18 has a cylindrical outerwall 26 and a radially inwardly extending leg 28. The metal reinforcingring structure 18 is shown covered at least in part with the elastomericseal material 20 on a radially outwardly facing surface of the outerwall 26 which may be contoured with undulations 30 to provide a snug andfluid tight installation in the bore 14 of the crankcase 16. Theelastomeric seal material of the seal body 22 extends along the radiallyinwardly extending leg 28 of the metal core 18 on the air side A of theleg 28 and extends around an inner end 32 to cover a portion of the oilside O of the leg 28 to provide a central portion 23 of the seal body 22radially inward from the leg 28. The core 18 and seal body 22 arerelatively rigid, yet the seal material 20 is sufficiently resilient toform the seal lip 24.

The seal lip 24, when in the relaxed, uninstalled state (FIG. 2),extends in a slightly inclined orientation, such as between about 1-10degrees from a horizontal central axis 33 of the seal 10, and has anannular, radially inwardly facing sealing surface 34 and an opposite,radially outwardly facing backing surface 36 extending between an oilside end 38 and a free air side end 40. The sealing surface 34, while inits free state, has a maximum diameter SD at the oil-side end 38 that isless than an outer diameter OD of a running surface 35 of the shaft 12(FIGS. 3-5), and thus, the entire sealing surface 34 is assured of beingbrought into sealing engagement with the running surface 35 uponcompleting installation assembly and while in use. The sealing surface34 can be configured having hydrodynamic features 41 in the form of ribsor a thread, that act to pump oil back to the oil side O of the seal 10during rotation of the shaft 12. Further, the air side end 40 can beprovided with a dust exclusion lip 39 that facilitates prevention ofcontamination ingress from the air-side A to the oil-side O of the sealassembly 10, and further, facilitates maintaining the lubricant on theoil-side O of the assembly 10. The seal lip 24 is formed having apredetermined thickness t1 (shown only in FIG. 1 to avoid cluttering theFigures, as with other dimensional features discussed hereafter) tofacilitate maintaining the low-torque seal against the shaft 12, as isdiscussed in more detail below.

An annular bridge 42 operably connects the seal lip 24 to the seal body22. The annular bridge 42 is connected to the oil side end 38 of theseal lip 24 by a first hinge 44 and to the central portion 23 of themounting portion 18 by a second hinge 46. The bridge 42 extends over alength L1 generally along an imaginary line 45 that extends between andthrough the hinges 44, 46 at an angle to the horizontal central axis 33,such as between about 20-40 degrees, though the angle can range from1-89 degrees from horizontal. The second hinge 46 transitions to anorientation that is about parallel with the radial leg 28 of themounting portion 18 and about perpendicular to a horizontal axis H ofthe seal 10. The bridge 42 extends from the first hinge 44 to the secondhinge 46 in radially overlying relation to the seal lip 24, and thus,provides an annular pocket 48 facing the air-side A of the seal assembly10. The bridge 42 is constructed having a thickness t2, while the firstand second hinges 44, 46 are constructed having respective thickness t3,t4. The relative thicknesses are preferably such that t1>t3; t2>t3, andt2>t4, and more preferably, t1>t3; t2>t3, and t2>t4. In addition, whilein the free state, the first hinge 44 has a first diameter H1D and thesecond hinge 46 has a second diameter H2D, wherein H1D<H2D.

The seal 10 further has a projection 50, that extends generally from thefirst hinge 44 axially away from the seal lip 24 and the bridge 42toward the oil side O of the seal 10. The projection 50 is configured toaid in the oil-side installation, discussed further below, to preventthe seal lip 24 and bridge 42 from unfolding during installation.Further, the projection 50 is configured to remain out of contact withthe shaft running surface 35 upon installation and during use. In theevent the oil side O experiences a pressure change, such as a negativepressure (relative vacuum), the pressure differential across the sealexerts an axially inward force on the seal 10, whereupon the projection50 acts at least in part to stiffen the seal lip 24, and thus, acts toprevent the seal lip 24 from lifting out of sealing contact from theshaft running surface 35. The projection 50 has a main thicknessextending between a radially inwardly facing inner surface 52 and aradially outwardly facing outer surface 54 that is sufficient tosubstantially retain its shape and geometry during installation withoutallowing the projection 50 to roll back or under itself. To facilitatesmooth installation, the inner surface 52 is shown to gradually taperradially outwardly toward a radially outermost free end 56, and isfurther shown as having a convex contour, by way of example and withoutlimitation. To further facilitate smooth installation, a pluralitycircumferentially spaced skids, also referred to as projection ribs,skid ribs or ribs 53, extend axially along the inner surface 52 betweenthe seal lip 24 and the free end 56, shown as tapering gradually towardthe free end 56. The ribs 53 are preferably spaced equidistant from oneanother about the circumference of the seal lip 24 and extend radiallyinwardly from the inner surface 52 a predetermined distance torelatively narrow contact edges 55 that function as “low friction” skidsduring installation. By “low friction”, what is meant is that thefriction between the projection 50 and the shaft 12 would be increasedif the ribs 53 were not present. As mentioned, the ribs 53 remain out ofcontact with shaft running surface 35 upon installation and during use.Accordingly, the inner surface 52 and ribs 53 have a minimum diameter PDthat is at least slightly greater than the inner diameter SD of thesealing surface 34 of the seal lip 24, and thus, as mentioned, uponassembly on the shaft 12, the inner surface 52 and ribs 53 remain spacedradially outwardly, and out of contact, from the running surface 35. Theprojection 50 has a length L2 that extends generally from the firsthinge 44 and/or the oil-side end 38 of the seal lip 24 that issufficient to counter any forces tending to invert bridge 42, whereinthe length L2 is less than the length L1 of the bridge 42. The ribs 53extend along the entire or substantially the entire length L1 of theprojection 50. As such, the projection 50 acts primarily duringinstallation as an aid to prevent the seal lip 24 from attaining another than proper configuration on the shaft 12, while the ribs 53prevent the full inner surface of the projection 50 from contacting theshaft. As such, the ribs 53 reduce the amount of contact with the shaft12, and thus, reduce the friction generated against the shaft 12 duringinstallation, thereby further preventing the seal lip 24 from inverting.As further shown in FIG. 2, the projection 50 is formed substantiallyabove the imaginary line 45, which further enhances the ability of theprojection 50 and ribs 53 to function as an “anti-inversion” feature forthe seal bridge 42. In addition, the projection 50 and ribs 53 extendaxially inwardly toward the oil-side O from an imaginary line 47extending perpendicular to the imaginary line 45 through the first hinge44.

FIGS. 3-5 illustrate an oil-side installation progression of the shaft12 through the seal 10, wherein a central axis 57 of the shaft 12 isslightly misaligned with the central axis 33 of the seal 10 (FIGS. 3-4)and then coaxially aligned in FIG. 5. In this installation, the seal 10is already installed into the housing 16, with the shaft 12 thereafterbeing extended into the bore 14 and through the seal 10. As the shaft 12is slid axially into the bore 14, an end 58 of the shaft 12 initiallyengages at least some of the contact edges 55 of the projection ribs 53.To facilitate assembly, the end 58 of the shaft 12 is configured toprovide a lead-in tapered surface 60. With the shaft 12 and seal 10being axially misaligned, it should be recognized that the diametricallyopposite sides (not shown) of the seal and shaft are shifted relative toone another accordingly, and thus, a slight gap could result initiallybetween the shaft 12 and projection ribs 53. As shown in FIG. 4, as theshaft 12 progresses axially though the seal 10, the contact edges 55 ofthe ribs 53 remain in contact with the shaft 12 as they slide over theshaft tapered lead-in surface 60 onto the running surface 35. As this isoccurring, the main seal lip 24 is caused to expand radially outwardlyand the air-side end 40 of the seal lip 24 is caused to pitch radiallyoutwardly, such that the pocket 48 is caused to partially collapse,thereby reducing the axial installation force required to install theseal 10 about the shaft 12. As such, the projection 50 and the ribs 53act to bring the seal lip 24 into axial alignment with the shaft 12. Inaddition, aside from bringing the seal lip 24 into axial alignment withthe shaft 12, the projection 50, having its predetermined length L2,acts as a lever arm to counter any torsion forces generated between theseal 10 and the shaft 12 from acting on the bridge 42, while thecircumferentially spaced ribs 53 act to prevent the inner surface 52 ofthe projection 50 from contacting the shaft 12. Thus, the amount offriction generated against the shaft 12 is minimized, thereby preventingthe bridge 42 from being rolled and inverted axially outwardly towardthe air-side A of the seal 10. Accordingly, as shown in FIG. 5, uponfull installation of the shaft 12 through the seal 10, the seal lip 24attains its proper sealing configuration with the running surface 35 ofthe shaft 12, while the projection 50 and the contact edges 55 of theribs 53 remain spaced radially outwardly from contact with the shaftrunning surface 35.

FIG. 6 illustrates a seal 110 constructed in accordance with anotheraspect of the invention, with FIGS. 7-12 illustrating the seal 110 beinginstalled in an oil-side installation progression on a shaft 112,wherein the same reference numerals as used above, offset by a factor of100, are used to identify similar features as discussed above. Asdiscussed above, the seal 110 has a mounting portion, shown here, by wayof example and without limitation, as having a rectangular metalreinforcing ring structure 118 in cross-section and an elastomeric sealmaterial covering 120, wherein the covering 120 is shown as being moldedto encapsulate the ring structure 118. Similarly as discussed above, thematerial covering 120 is shown having an outer contoured surface withradially outwardly facing ribs for snug and fluid tight installation ina bore 114 of a housing 116.

The elastomeric seal material 120 provides a seal body 122 that extendsradially inwardly of the core 118 to a central vertically extending bodyportion 123. Similarly as in the seal 10 discussed above, the seal 110has a seal lip 124 and a bridge 142 with a first hinge 144 connectingthe seal lip 124 to the bridge 142 and a second hinge 146 connecting thebridge 142 to the central portion 123 of the seal body 122. The relativethicknesses (FIG. 6) of the seal lip t1; bridge t2 and the first andsecond hinges t3, t4, respectively, are as discussed above. Further, therelative diameters H1D, H2D of the first and second hinges 144, 146 alsoremain as discussed above. Accordingly, thus far, other than theconfiguration of the mounting portion 118, the seal 110 is the same asthe seal 10.

The notable distinction between the seal 110 and the previouslydiscussed seal 10 can be seen with the location of a projection 150 andits associated ribs 153 on the seal 110. With regard to the seal 110,the projection 150 and the ribs 153 extend from a more radially outwardlocation than the previously discussed projection 50 and ribs 53,however, the projections 50, 150 and ribs 53, 153 remain similarlyshaped. Thus, the projection 150 and ribs 153 extend generally from thefirst hinge 144 axially away from the seal lip 124 and the bridge 142toward the oil side O of the seal 110, however, in contrast to theprevious embodiment, they extend entirely or substantially entirelyradially outwardly relative to the first hinge 144. As with thepreviously discussed projection 50, the projection 150 has a thicknessextending between an inner surface 152 and outer surface 154 that issufficient to substantially retain its shape and geometry duringinstallation without allowing the projection 150 to roll under or backon itself. To facilitate smooth installation, the inner surface contactedges 155 of the ribs 153 are gradually tapered to diverge radiallyoutwardly, and are further shown as having a convex contour extendingradially outwardly to or immediately adjacent to a free end 156 of theprojection 150. The inner surface 152 and contact edges 155 have aminimum diameter PD that is at least slightly greater than the innerdiameter of a sealing surface 134 of the seal lip 124, and thus, asdiscussed above with regard to the projection 50, and ribs 53, uponassembly on the shaft 112, the inner surface 152 and contact edges 155are spaced radially outwardly out of contact from the shaft runningsurface 135. The projection upper or radially outwardly facing outersurface 154 extends in a smooth transition from the bridge 142 asufficient length L2 to counter any forces tending to invert bridge 142,wherein the length L2 is less than the length L1 of the bridge 142. Assuch, as with the projection 50 discussed above, the projection 150 andribs 153 extending therealong act primarily during installation toprevent the seal lip 124 from attaining an other than properconfiguration on the shaft 112. Further, even more so than theprojection 50, the projection 150 and ribs 153 are formed entirely abovean imaginary line 145 extending between the first and second hinges 144,146, which further enhances the ability of the projection 150 tofunction as an “anti-inversion” lever arm feature for the seal bridge142. In addition, the projection 150 extends axially inwardly toward theoil-side O from an imaginary line 147 extending perpendicular to theimaginary line 145 through the first hinge 144. As discussed above, thedimensional aspects of the projection 150, including its insidediameter, thickness and length provide its ability to prevent the bridge142 from becoming inverted during assembly.

FIGS. 7-12 illustrate an oil-side installation progression of the shaft112 through the seal 110, wherein a central axis 157 of the shaft 112 iscoaxially aligned with the central axis 133 of the seal 110. In thisinstallation, the seal 110 is already installed into the housing 116,with the shaft 112 thereafter being extended into the bore 114 andthrough the seal 110. As the shaft 112 is slid axially into the bore114, a tapered end 158 of the shaft 112 initially engages the oil-sideend 138 of the seal lip 124. This occurs because the radially inwardlyfacing inner surfaces of the projection ribs 153, having a largerdiameter than the shaft 112, are radially outward from the shaft 112,and thus, do not make initial contact with the shaft 112. The engagementof the end 138 of the seal lip 124 with the end 158 of the shaft 112causes the seal lip 124 to pitch radially outwardly, such that thepocket 148 is caused to partially collapse, while simultaneously causingthe projection 150 to pitch radially inwardly. The pitching motions arefree to continue until the contact edges 155 of the ribs 153 engage theouter surface of the shaft 112, whereupon the stiffness of theprojection 150 substantially prevents any further pitching. As such, thenarrowly profiled contact edges 155 are caused to slide with minimalcontact and frictional engagement along the shaft 112, as shown in theseries of progression views, until the sealing surface 134 is fullyreceived on the shaft 112, at which time, the contact edges 155 of theribs 153 move out of contact from the shaft 112 and remain out ofcontact with the shaft 112 during use.

FIGS. 13-19 illustrate an oil-side installation progression of the shaft112 through the seal 110 that follows the same progression as describedfor FIGS. 6-11, however, the central axis 157 of the shaft 112 isaxially misaligned with the central axis 133 of the seal 110. As theshaft 112 is slid axially into the bore 114, a tapered end 158 of theshaft 112 initially engages at least some of the ribs 153, which slidealong the tapered end 158 until they contact the running surface 135 andthe end 138 of the seal lip 124 engages the end 158 of the shaft 112.The engagement of the end 138 of the seal lip 124 with the end 158 ofthe shaft 112 causes the seal lip 124 to pitch radially outwardly, suchthat the pocket 148 is caused to partially collapse, whilesimultaneously causing the projection 150 to pitch radially inwardlywith the ribs 153 maintaining contact with the running surface 135. Theribs 153 are caused to slide along the shaft 112, as shown in the seriesof progression views, and when the seal lip 124 is fully received on theshaft 112, the ribs 153 move radially outwardly with the projection 150such that they remain out of contact from the shaft 112, as shown inFIG. 19

FIGS. 20 and 21 illustrate a seal 210 constructed in accordance withanother aspect of the invention, with FIGS. 22-24 illustrating the seal210 being installed in an oil-side installation progression on a shaft212, wherein the same reference numerals as used above, offset by afactor of 200, are used to identify similar features as discussed above.The seal 210 is constructed generally the same as discussed above withregard to FIG. 6, including a mounting collar 218 contoured withradially outwardly facing ribs for snug and fluid tight installation ina bore 242 of the crankcase housing 216. Further, a seal body 222extends radially inwardly from the core 218 to a central verticallyextending body portion 223. The seal 210 has a seal lip 224 and a bridge242 with a first hinge 244 connecting the seal lip 224 to the bridge 242and a second hinge 246 connecting the bridge 242 to the central portion223 of the seal body 222. The relative thicknesses of the seal lip t1;bridge t2 and the first and second hinges t3, t4 are as discussed above.Further, the relative diameters H1D, H2D of the first and second hinges244, 246 also remain as discussed above. Accordingly, thus far, otherthan the configuration of the mounting portion 218 and the seal 210 isthe same as the seal 110. In addition, a projection 250 and a pluralityof circumferentially spaced ribs 253 extending radially inwardly fromthe inner surface 252 of the projection 250 extend generally from thefirst hinge 244 and the bridge 242 toward the oil side O. The projection250 has thickness extending between the inner surface 252 and outersurface 254, wherein the projection 250 and ribs 253 are shapedgenerally the same as that discussed with regard to the previouslydiscussed projections 50, 150 and ribs 53, 153. The inner surface 252and contact edges 255 of the ribs 253 have a minimum diameter PD that isgreater than the maximum inner diameter of a sealing surface 234 of theseal lip 224, and thus, as discussed above with regard to the projection50, 150, upon assembly on the shaft 212, the ribs 253 are spacedradially outwardly out of contact from the shaft running surface 235.The projection outer surface 254 extends in a smooth transition from thebridge 242 a sufficient length L2 to counter any forces tending toinvert bridge 242, wherein the length L2 is less than the length L1 ofthe bridge 242, as discussed with regard to seal 110.

The notable distinction between the seal 210 and the previouslydiscussed seal 110 can be seen with the addition of a plurality ofstiffening ribs 60 molded as one piece of material with the seal body222. The stiffening ribs 60 facilitate assembly and to maintain asealing surface 234 of the seal lip 224 in proper sealing relation withthe running surface 235 of the shaft 212 during and upon assembly. Thestiffening ribs 60 extend axially along the bridge 242, and are shownhere as extending along the upper or outer surface 254 of the projection250 and along the full length of the bridge 242 and terminating at thecentral body portion 223 of the seal body 222. The stiffening ribs 60can be provided in any suitable number sufficient to prevent reversefolding of the bridge 242 and the main seal lip 224 during assembly, andare shown in FIG. 20, as being about 60 stiffening ribs 60, by way ofexample and without limitation, spaced in radial alignment opposite acorresponding number of the skid ribs 253. Each stiffening rib 60 isspaced circumferentially from an adjacent stiffening rib 60, with thestiffening ribs 60 being spaced equidistant from one another about thecircumference of the seal body 222. The height of the stiffening ribs 60is such that an uppermost surface 62 of the stiffening ribs 60 remainspaced from the seal body 222 upon being assembled. As such, thestiffening ribs 60 do not interfere with the ability of the second hinge246 to flex in use.

An oil side installation progression of the shaft 212 through the seal210 is generally the same as discussed with regard to FIGS. 7-12 for aco-axially aligned installation, and the same as discussed with regardto FIGS. 13-19 for an axially misaligned installation. However, as theseal assembly 210 is moved axially onto to the shaft 212, and when thecontact edges 255 of the skid ribs 253 engage the shaft 212, thestiffening ribs 60 are placed under slight tension and act to preventthe seal lip 224 and bridge 242 from inverting and unfolding. Further,the stiffening ribs 60 add rigidity to the projection 250, which furtherenhances the ability of the seal lip 224 to be maintained in sealingengagement with the shaft 212, such as when a vacuum is established onthe oil-side O of the seal 210. As such, the seal lip 224 is assured ofbeing maintained in a proper sealing orientation on the shaft 212 duringand upon completion of the assembly process.

FIG. 25 illustrate a portion of a seal 310 constructed in accordancewith another aspect of the invention, wherein the same referencenumerals as used above, offset by a factor of 300, are used to identifysimilar features as discussed above.

The seal 310 is similar to the seal 210, wherein all the features arethe same with the exception that a plurality of gaps 64 extend axiallyinto a projection 350, thereby providing a plurality of radially spacedprojections 350 spaced radially from one another by the gaps 64. Thegaps 64 and projections 350 are provided in uniformly spaced relationand size, thereby providing the seal 310 having a circumferentiallysymmetric appearance. The gaps 64 extend axially from an oil-side end ofthe seal lip 324 through to free ends 356 of adjacent projections 350.In the embodiment shown in FIG. 25, the gaps 64 occupy between about20-50 percent of the total circumference (gaps 64+projections 350) ofthe seal body 322, though the percent could be varied, as desired. Thegaps 64 provide enhance radial flexibility to the individually spacedprojections 350 during assembly by allowing the projections 350 to flexindividually relative to one another. The embodiment illustrated showseach individual projection 350 having a radially inwardly extending skidrib 353, wherein the skid ribs 353 and their associated narrowlyprofiled contact edges 355 function to minimize the friction generatedagainst the shaft 312 during the oil-side installation process, asdiscussed above. In the embodiment shown, by way of example, each of theprojections 350 also has one of the stiffening ribs 360 extendingcentrally along the upper surface of the projections 350 to enhancetheir stiffness, though it should be recognized that fewer stiffeningribs 360 could be used, depending on the application, thereby leaving atleast some of the projections 350 without ribs.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims and any claimsultimately allowed, the invention may be practiced otherwise than asspecifically described.

1. A radial shaft seal configured for receipt in a housing and about ashaft to sealingly isolate an air side of the shaft seal from an oilside of the shaft seal, comprising: an annular mounting portion; a seallip having an annular sealing surface extending between an oil side endand a free air side end, said sealing surface being configured to extendaxially relative to the shaft; an annular bridge connected to said oilside end of said seal lip by a first hinge and to said mounting portionby a second hinge, said bridge extending from said first hinge to saidsecond hinge in radially overlying relation to said seal lip; at leastone projection extending from said first hinge away from said bridgetoward said oil side of said seal, said at least one projection having aradially outwardly facing outer surface and a radially inwardly facinginner surface; and a plurality of circumferentially spaced ribsextending radially inwardly from said inner surface.
 2. The radial shaftseal of claim 1 wherein said ribs have an inner minimum diameter andsaid sealing surface has an inner maximum diameter, said minimumdiameter being greater than said maximum diameter.
 3. The radial shaftseal of claim 2 wherein said seal lip has a radially outwardly facingsurface with a maximum diameter and said minimum diameter of said ribsis greater than said outwardly facing maximum diameter of said seal lip.4. The radial shaft seal of claim 1 wherein said at least one projectionhas a length extending away from said first hinge and said ribs extendsubstantially along said length of said at least one projection.
 5. Theradial shaft seal of claim 1 further comprising a plurality ofcircumferentially spaced stiffening ribs extending axially along saidouter surface of said at least one projection and said bridge.
 6. Theradial shaft seal of claim 1 wherein said at least one projection iscircumferentially continuous.
 7. The radial shaft seal of claim 1further comprising a plurality of said projections spaced from oneanother by gaps.
 8. The radial shaft seal of claim 7 wherein each one ofsaid projections has a separate one of said ribs.
 9. The radial shaft ofclaim 8 wherein an upstanding stiffening rib extends axially along saidbridge and along at least some of said outer surfaces of saidprojections.
 10. The radial shaft seal of claim 9 wherein saidstiffening ribs extend along each of said projections.
 11. A radialshaft seal assembly, comprising: a shaft extending along a central axisand providing a running surface with a predetermined diameter; and aradial shaft seal configured for receipt in a housing and about saidshaft to sealingly isolate an air side of the radial shaft seal from anoil side of the radial shaft seal, comprising: an annular mountingportion; a seal lip having an annular sealing surface and an oppositebacking surface extending between an oil side end and a free air sideend, said sealing surface being configured to extend axially in dynamicsealing contact with said running surface; an annular bridge attached tosaid oil side end of said seal lip by a first hinge and to said mountingportion by a second hinge, said bridge extending from said first hingeto said second hinge in radially overlying relation to said seal lip; atleast one projection extending axially from said first hinge toward saidoil side of said seal, said at least one projection having a radiallyoutwardly facing outer surface and a radially inwardly facing innersurface; and a plurality of circumferentially spaced ribs extendingradially inwardly from said inner surface.
 12. The radial shaft sealassembly of claim 11 wherein said at least one projection has a lengthextending away from said first hinge and said ribs extend substantiallyalong said length of said at least one projection.
 13. The radial shaftseal assembly of claim 11 further comprising a plurality ofcircumferentially spaced stiffening ribs extending axially along saidouter surface of said at least one projection and said bridge.
 14. Theradial shaft seal assembly of claim 11 wherein said at least oneprojection is circumferentially continuous.
 15. The radial shaft sealassembly of claim 11 further comprising a plurality of said projectionsspaced from one another by gaps.
 16. The radial shaft seal assembly ofclaim 15 wherein each one of said projections has a separate one of saidribs.
 17. The radial shaft assembly of claim 16 wherein an upstandingstiffening rib extends axially along said bridge and along at least someof said outer surfaces of said projections.
 18. The radial shaft sealassembly of claim 17 wherein said stiffening ribs extend along each ofsaid projections.
 19. The radial shaft seal assembly of claim 11 whereinsaid ribs are spaced radially outwardly out of contact from said runningsurface of said shaft.
 20. A method of installing a radial shaft sealonto a shaft, comprising: providing a shaft having a running surface;providing the radial shaft seal with a seal lip having an annularsealing surface converging from an oil side end to a free air side endwhile in a free state with an annular bridge attached to the oil sideend by a first hinge and diverging to a second hinge while in the freestate, the second hinge being attached to an outer mounting portion suchthat the bridge extends in radially overlying relation with the seallip, the seal further including at least one projection extendingaxially from the first hinge toward an oil side of the seal and aplurality of circumferentially spaced ribs extending radially inwardlyfrom the projection; moving the shaft and the radial shaft seal axiallytoward one another; bringing the oil side end of the seal lip intoabutment with an end of the shaft; bringing at least some of the ribsinto contact with running surface of the shaft; and bringing the sealingsurface into sealing engagement with the running surface andsimultaneously moving the ribs out of contact with the running surface.